This invention relates to internal combustion engines and, more particularly, to diesel engines including particulate traps in the exhaust system. Still more particularly, this invention relates to methods and apparatus for sensing the regeneration of such particulate traps.
In internal combustion engines such as diesel engines, various particles are present in the exhaust gases as a result of incomplete combustion. It is not desirable to discharge these particles into the atmosphere and a known method of preventing such undesirable discharge is to provide the exhaust system of the engine with a particulate trap, or filter, which intercepts and collects the particles.
It is also well know that, from time to time, the particulate trap should be regenerated and this can be done using one of several well known procedures. In the regeneration process, the entrapped particles are burned off the trap and the products of that combustion are allowed to pass through the exhaust system to the atmosphere. Although the products of regeneration are further broken down from what results in the power combustion cycle, this can still generate pollutants. For that reason, it is desirable for the regeneration control system, and possibly the operator of the vehicle, to know when regeneration of the particulate trap is occurring, i.e., beginning and ending. A known type of regeneration sensor measures the pressure differential across the particulate trap, but such sensors are expensive and are not very accurate.